Having previously demonstrated the ability to build collagen-like self-templating supramolecular structures out of M13 phage filaments, this year the Seung-Wuk Lee Lab has come out with a new paper demonstrating their ability to use those structures as a litmus to sensitively detect things like humidity, volatile organic compounds, or TNT explosives and report color strongly enough for an iPhone camera to distinguish:

Biomimetic virus-based colourimetric sensors
Many materials in nature change colours in response to stimuli, making them attractive for use as sensor platform. However, both natural materials and their synthetic analogues lack selectivity towards specific chemicals, and introducing such selectivity remains a challenge. Here we report the self-assembly of genetically engineered viruses (M13 phage) into target-specific, colourimetric biosensors. The sensors are composed of phage-bundle nanostructures and exhibit viewing-angle independent colour, similar to collagen structures in turkey skin. On exposure to various volatile organic chemicals, the structures rapidly swell and undergo distinct colour changes. Furthermore, sensors composed of phage displaying trinitrotoluene (TNT)-binding peptide motifs identified from a phage display selectively distinguish TNT down to 300 p.p.b. over similarly structured chemicals. Our tunable, colourimetric sensors can be useful for the detection of a variety of harmful toxicants and pathogens to protect human health and national security.

“Bioinspired phage-based colourimetric sensors, termed Phage litmus, are composed of hierarchical bundles like the collagen fibres in turkey skins. Application of target molecules (chemical stimuli) causes colour shifts due to structural changes, such as bundle spacing (d₁ and d₂) and coherent scattering. Using a handheld device’s camera (iPhone) and home-built software (iColour Analyser), we can identify target molecules in a selective and sensitive manner.”